This invention relates to the pelletizing of particulate food materials to produce pelletized food products having unique properties and characteristics. More particularly, the invention relates to the production of porous, cellular pelletized food products having a crisp, crunchy, friable texture, and the use of such porous pellets in food products.
The process of agglomerating powdered food solids to increase its wettability in water has been used for many years. In such procedures, powdered materials are converted to irregularly shaped, random aggregates or clumps which are capable of more rapid solution than in the powered form. Typically, an edible food powder is introduced into the upper portion of a treatment chamber, where the falling particles are contacted with finely atomized water and saturated steam whereby moisture is distributed on the surfaces of the falling particles, with the particles acquiring a surface stickiness. Sufficient comingling of the falling particles takes place whereby the particles adhere together in the form of porous random aggregates which typically have a particle size such that the bulk of the aggregate will pass through a 20 mesh screen (0.84 mm) but remain on an 80 mesh screen (0.177 mm). Such a process, which is commonly referred to as "instantizing", is used in the production of aggregates of a variety of powdered edible materials such as skim milk powder, gelatin, pectin, starch, lactose, coffee, yeast and egg whites, as disclosed in U.S. Pat. Nos. 2,835,586; 2,851,364; 2,856,288; 2,856,290; 2,856,318; 2,897,084; 2,921,854; and 2,950,204, respectively. However, the aggregates or clusters formed by such a process tend to be relatively weak and fragile, and readily crumble and break up if subjected to rough or mechanical handling.
Also, a number of particulate food materials such as powdered flour, cocoa, cane sugar and dried milk are produced in granular form on a conventional pelletizing disc in order to increase the particle size of the material and to reduce the amount of fines usually associated with the handling of such powdered materials. In such an operation, the material, in finely divided form, is deposited on the surface of an inclined, rotating disc where it is contacted with water or a binder solution and maintained on the disc until the desired granule size is obtained. The pelletized products thus formed are relatively hard, dense and non-porous and typically are about 3 mm. in size. Such pelletized food products generally are soluble in water and are used in applications in which solubility in water is in essential requirement.